Since the invention of the integrated circuit, the semiconductor industry has experienced rapid growth due to improvements in the integration density of a variety of electronic components (e.g., transistors, diodes, resistors, capacitors, etc.). This improvement in integration density has come from shrinking the semiconductor process node (e.g., shrink the process node towards the sub-20 nm node). As the demand for miniaturization continues, the further shrinking of the process node may increase the complexity of fabricating integrated circuits.
As semiconductor technologies evolve, semiconductor fabrication processes have become more sophisticated and hence require complex equipment and fixtures. In the semiconductor process, integrated circuits are fabricated on a semiconductor wafer. The semiconductor wafer goes through many processing steps before a plurality of integrated circuits are separated by cutting the semiconductor wafer. The processing steps may include lithography, etching, doping and depositing different materials.
Ion implantation is a processing technique for doping different atoms or molecules into a wafer. By employing ion implantation, the majority charge carrier may be altered so as to produce regions in the wafer having different types and levels of conductivity. In an ion implanter, an ion generator may generate an ion beam and direct the ion beam towards the target wafer. In accordance with the cross section of ion beams, ion implantation processes may be divided into two categories, namely a ribbon beam with a rectangular cross section and a spot beam with a circular cross section.
Furthermore, in order to achieve a uniform ion distribution on the target wafer, either the wafer to be implanted or the ion beam is scanned. In accordance with the scanning pattern, ion implantation processes may be divided into two categories, namely a one-dimensional (1-D) ion implantation scan or a two-dimensional (2-D) ion implantation scan. In addition, a variety of ion implantation monitoring systems may be employed to characterize ion beams before an ion implantation process occurs. However, an unexpected fluctuation in the ion beams may cause a non-uniform ion distribution in the target wafer.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale.